Dry explosive composition containing particulate metal of specific mesh and gauge



9 Claims ABSTRACT OF THE DISCLOSURE A novel dry explosive compositionconsisting essentially of: ammonium nitrate as oxidizer and aparticulate light metal as fuel, said metal being within the rangesubstantially of from about No. 4 to about No. 200 mesh and having agauge of from about 0.25 mil to about 40 mils. Other inorganicoxidizers, fuels and explosive sensitizers can be incorporated into thecomposition.

CROSS-REFERENCES TO RELATED APPLICATIONS This application is acontinuation-in-part of application Ser. No. 603,762, now abandonedfiled Dec. 22, 1966, which in turn was a continuation-in-part ofapplication Ser. No. 419,262, filed Oct. 16, 1964, now U.S. Patent No.3,307,986, which in turn was a continuation-in-part of application Ser.No. 299,115, filed July 31, 1963, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to explosives andmore particularly is concerned with a novel dry explosive compositionexhibiting high energy which gives reliable, uniform energy releasesfrom batch to batch. The terms dry mix, dry explosive, dry compositionand dry explosive composition as used herein are to be taken in theirgenerally accepted meaning in the explosive art and refer to explosiveswhich are granular or thick, paste-like in nature and have substantiallyno free liquid phase thereby differentiating from the slurry typeblasting compositions. These dry mixes are further characterized asbeing non-pumpable.

Dry, granular explosives based on ammonium nitrate, e.g. the common ANFOcompositions containing generally about 94 weight percent prilledammonium nitrate and about 6 weight percent fuel oil, have been usedcommercially for a number of years. These are satisfactory for manyblasting operations but suffer from the disadvantages that they do notpropagate in diameters smaller than about 1 inch and they have arelatively low bulk density of about 0.8 gram/cc.

The addition of other fuels and/ or sensitizers to such ammoniumnitrate-fuel oil compositions has helped to upgrade the resultingproduct with respect to sensitivity, propagation and explosive work orpower output. Commonly, light metals such as magnesium, aluminum,magnesium-aluminum binary alloys, magnesium silicide, aluminum silicideand other magnesium alloys and aluminum alloys have been used as fuelsand/or sensitizers. Additionally, other carbon containing materialsincluding conventional explosives, such as nitrostarch dinitrotoluene,trinitrotoluene and the like, as well as carbon black, sugars, molasses,etc. have been used to upgrade the ammonium nitrate-fuel oilcompositions.

nited States Patent As indicated hereinbefore, such additions haveupgraded the performance of such dry mixes, but there still remains theproblem that such mixes may not always give high energies of predictablehigh levels and rapid detonation rates.

SUMMARY It is a principal object of the present invention to provide animproved dry explosive composition possessing high energy whichcomposition provides reliable high energy release upon detonation.

This and other objects and advantages readily will become apparent fromthe detailed description presented hereinafter.

In general the improved explosive composition of the present inventioncomprises ammonium nitrate or ammonium nitrate in admixture with aninorganic alkali metal oxygen containing oxidizing salt or mixtures ofsuch salts as oxidizer and a light metal fuel of predetermined mesh andgauge characteristics. Additionally, the composition can contain othernon-detonable organic fuels, detonable explosive sensitizers, thickeningagents and the like to assure the preparation of an explosivecomposition of predetermined characteristics.

These compositions are suitable for use in any of a wide variety ofblasting operations including open pit and underground ore mining, hardrock mining and excavating operations, construction, demolition and thelike operations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Usually the present dryexplosive composition comprises on a weight basis:

(a) Particulate ammonium nitrate from about 50 to about 97 percent,

(b) Particulate light metal from about 3 to about 50 percent, said lightmetal ranging substantially from about No. 4 to about No. 200 mesh US.Standard Sieve and having a gauge of from about 0.25 mil to about 40mils.

(c) Particulate alkali metal nitrate, chlorate, perchlorate or mixturesthereof up to about 40 percent,

(d) Non-detonable organic fuel up to about 10 percent, and

(e) A gelling and/or thickening agent up to about 2.5 percent.

In a preferred embodiment, the present novel dry explosive compositioncomprises on a weight basis:

(a) Particulate ammonium nitrate from about to about 55 percent,

(b) Particulate aluminum, magnesium, magnesium alloys, aluminum alloysor mixtures thereof within the mesh and gauge ranges set forthhereinbefore from about 5 to about 40 percent,

(c) Sodium nitrate up to about 20 percent,

(d) Non-detonable liquid hydrocarbon up to about 6 percent, and

(e) Natural gum and/or synthetic polymeric thickening agent up to about1 percent.

The dry explosive compositions may also contain up to about 16 percentof deton-able organic sensitizers.

The uniqueness, novelty and unexpected useful results realized with thepresent invention resides in the use of a particulate light metal havinga predetermined mesh size and gauge (thickness). For operability thelight metal to be employed in the present composition rangessubstantially from about No. 4 to about No. 200 mesh (US.

7 Standard Sieve) and has a gauge of from about 0.25 mil to about 40mils. The term mil is used in its usually accepted definition of being0.001 of an inch.

Ordinarily, the light metal employed has a particle size distributionwithin the broad range specified wherein from about 25 to about 60percent is larger than No. 50 mesh, the balance being substantially No.50 to No. 100 mesh wherein from about 15 to about 100 percent of theparticles have a gauge of from about 0.25 mil to about 4 mils and up toabout 85 percent have a gauge of from about 4 to about 15 mils.Preferably, metal with a gauge of less than about 10 mils is employed.However, to obtain specific characteristics with a given explosivecomposition, various blends of metal within the mesh and gauge sizeranges set forth herein can be employed in predetermined size ranges. Byemploying particulate metals within the above defined particle size andgauge ranges a more powerful explosive composition can be prepared. Themetal particles as defined above will vary in shape from very thick(gauge) and coarse (mesh), to spherical (when mesh and gauge areapproximately the same) to straw like (long with a small gauge). Ingeneral the particles are nonequiaxed in shape. It is thought that theparticles having a smaller gauge perform similar to kindling in thatthey react very readily in the explosive reaction thus supplying thenecessary heat to efficiently burn the larger metal particles which inturn supply the necessary power and sustained heat in the explosivereaction. It appears that the use of metal particles within the welldefined size range allows for the production of a more powerfulexplosive over similar explosives wherein no gauge (thickness)limitations are placed on the metal particles. Also, the rate of theexplosive reaction can be adjusted by varying the ratio of kindling sizeparticles to coarser particles.

The term mesh or mesh size as applied herein to various materials meanssize determinations made by standard vibratory, controlled testprocedures. Since US. Standard Sieve Series was employed in the sizedeterminations of the present invention a certain No. mesh refers to thesieve designation. The size range of the metal particles in inches ormillimeters can be readily determined for example, from a standardconversion table such as the table on page 931, Langes Handbook ofChemistry, Revised 10th Edition.

It is understood that in certain instances because of manufacturingconditions or other circumstances, the particulate metal may contain asmall fraction up to 10 percent or more of metal passing a No. 200 meshsieve. Such additions have not been found to detrimentally affect theoperability of the present novel composition. This is particularly truein the case of some of the more brittle alloys; e.g., of themagnesium-silicon-aluminum type.

A typical aluminum metal employed in one of the embodiments of thepresent invention has a particle size and gauge distribution as setforth in Table I.

Table I Metal particle size, mesh Distribution, (U.S. Standard Sieve):percent NO. 30-50 60-70 No. 50-100 25-35 No. 100-150 about 5 Metalgauge, mils:

Up to 1 6-8 1 to 5 14-17 5-10 73-77 -15 3-7 15 .1

compositions limits set forth, a portion of the ammonium nitrate can bereplaced with sodium-, lithium-, potassiumor other alkali metal nitrate,-chlorate or -perchlorate salts, if desired, to obtain compositions ofvarying densities, sensitivities or other predetermined properties.Conveniently, prilled ammonium nitrate as presently employed in blastingcompositions has been found to be suitable in the practice of thepresent invention.

Small amounts of liquids such as petrolic liquids including naturalmineral oils and fractionated products from oil refining as well asother liquid organics having a favorable carbon-oxygen ratio such thatthere is no detrimental competition of the carbon with the metal foravailable oxygen in the systems can be used to promote component packingand also act as additional fuel. Also, a small amount of naturaloccurring water may be present such as that naturally absorbed by thenitrates present in the compositions. The quantities of such materialsat a maximum to be employed within the ranges disclosed herein are suchthat formation of separate liquid and solid phases is not realized andthe product is a dry composition; i.e. granular or pasty.

Fuel oil, kerosene and other liquid hydrocarbons, monohydroxy alkanolscontaining from 1 to about 4 carbon atoms, ethylene glycol, propyleneglycol, glycerol, formamide and mixtures thereof are particularlysuitable organic liquids for use in the present composition.

Additionally, finely divided solid carbonaceous fuels can beincorporated into the composition. These include, for example, saw dust,nut meats and flours, sugars, bogasse, powdered coke coals and charcoalsand the like.

If it is desired to impart water-resistivity to the composition, any ofa variety of water-resistant natural gums and synthetic gelling and/orthickening agents can be employed. Particularly suitable gums for use inthe present composition are the guar gums or mixtures of guar and karayagums. These materials not only impart a water resistance, desired formany operations, to the product but also readily are cross-linked to anypredetermined degree thereby providing a flow and non-rigidcharacteristic to the product when in thick paste-like form. Any of avariety of conventional crosslinking agents can be employed to achievethe crosslinking of the gum. The amount of crosslinking agent used issuch that the resulting water resistant explosive is pliable andgelatinous. To illustrate, with a guar gum, about 2.5 weight percent(based on gum weight) of a 5 percent sodium dichromate solution has beenfound to be a satisfactory agent for preparing the present composition.Likewise, a saturated solution of ammonium nitrate in liquid ammonia(Divers liquid) can be used. Conveniently, to aid dispersion of thislatter crosslinking material throughout the mix it can be diluted up toabout percent or more by volume with water.

Other sensitizers which can be incorporated into the composition, ifdesired, to impart certain characteristics to specific embodiments ofthe present novel explosive product include any of a wide variety ofconventional detonable organic explosive compounds such as, for example,nitrostarch, nitroglycerine, nitrotoluenes such as trinitrotoluene anddinitrotoluene, nitronaphthalene, trimethylolethane trinitrate,pentaerythritol tetranitrate, pentolites,cyclodinitrotrimethylenetetramine and the like.

The present novel product safely can be stored, shipped and handledeither in the bulk state or when placed in bags or other containers.Conveniently, for use in borehole blasting operations the product can beplaced in polyethylene or other easily deformable bags so as to providepreweighed units of material.

In use, the bagged materials can be directly inserted into a borehole,or for enlarged, chambered holes, e.g., the bags can be slit orotherwise opened before placing in the hole. This latter action assuresthat the explosive 6 composition will fill the borehole volume andgenerally No. 325 mesh and about 1 mil, and an ANFO (-94 conform withthe wall configuration of the hole. weight percent ammonium nitrate-6weight percent fuel Detonation of the explosive generally isaccomplished oil) composition, as controls.

TABLE I [Metal particulation, percent of total metal] Metal mesh size(U.S. sieve), metal gauge (mils) 25 to 35 15 to 25 to 1 to 10 l to 10 1Control 100 Control (ANFO) by conventional 'boosters and primers, shapedcharges TABLE TEST RESULTS and other high energy initiators.

The following examples will serve to further illustrate Run iggi ggE5132? 58%, the present lnventron, but are not meant to limit itthereto. (1 s./sq.m.) (KcaL/gmJ -la -la Example 1.A number of dry,granular explosive 21864 0 65 Q77 L 44 compositions were prepared usingvarious size and gauge 2,783 0 68 0.81 1. 48

2, 504 0. 61 0. 7s 1. 37 fractions of a particulate 40 welght percentmagnesium-6O 2,841 71 82 L 53 weight percent aluminum alloy blended witha mixture of gig g g; 8?? :3 particulate ammonium nitrate containing 94weight per- 21854 0 74 cent NH NO and 6 weight percent fuel oil. Eachcom- 2,623 0 62 0. 78 1. 41 2,933 0.69 0.80 1. 49 position contained ona weight basis 80 percent of the 2386 M8 0'79 L27 ammonium nitrate-fuel011 mixture and 20 weight per- 2,060 (H58 0.440 [L898 cent of themagnesium-aluminum alloy.

The mixes were made up in about 40 pound lots. About 20 pound sampleswere sealed in two-gallon Water resistant paint pails (total load about20 pounds), along with a one-third pound composition B detonatorattached to a strand of Primacord fuse line and the mixes tested in a:'standard underwater test. The detonator was placed inside the pail andthe Primacord extended out through the lid. Water resistance was assuredby a gasket sealing assembly where the Primacord came through the lid.

. the testing. Primacord was ccinnected to an The ammonium nitratecomponent consisted of about lmtiator and firlng line and the explosivecharge was 54 parts by Weight primed ammonium nitrate (Us.

detonated in a body of water at about half the depth Standard Sieve; +8meSh 2 7%, of a lake (mix placed at 42.5 feet beneath the surface of 52% +1 3g 7% 16/+2() h the water). The resulting pressure profile fromthe deto- 5.1%, 20/ +40 meshl.9%, -40 mesh0.2%) and nation was convertedinto electrical impulses by a piezobo t 46 parts by weight f crushedprilled ammonium electric gauge suspended in the water at the same levelnitrate (sieve analysis 8/+ l2 mesh0.8%, 12/ +16 a known horizontaldistance away from the charge. The mesh5.4%, 16/ +20 mesh-18.8%, 20/ +40electrical impulses were recorded and converted to the mesh-431%, me$hcorresponding pressures and from this the peak pressure, 325% shockenergy, bubble energy and total energy of the The fixtures were P p byblending the Ff explosive readily were calculated by methods describedPonents and Placmg, the resultmg composltlons in Underwater Explosives,H. Cole Princeton in sealed canisters for duplicate shots by thestandard University Press |(1948) underwater test following thetechnique and procedures described in Example 1. Tilble I presents themesh. and gauge of the Table III lists the metal alloy composition,particle particulate alloys employed 1n the compositions and mesh sizeand gauge of the metal component used in Table II summarlzes the resultsof underwater test shots each of the compositions Table IV presents theexplosive of H16 compositions of the Pmsent invention using Various testresults obtained for the mixes set forth in Table III.

metal gauges as well as a composition containing 100 The run numbers ineach of these tables identifies the percent of the metal all withinminus No. 200 to plus same explosive composition.

It is evident that all the compositions had a high peak pressure andtotal energy than either of the controls.

Example 2.A number of dry granular explosive compositions were preparedfrom particulate ammonium nitrate, fuel oil andmagnesiumsilicon-aluminum alloys. In each of these preparations the mixconcentration was about 86.4 Weight percent ammonium nitrate, about 3.6weight percent No. 2 fuel oil and about 10 weight percent of the alloy.

TABLE IIL-METAL COMPOSITION AND PARTICULAIION Alloy composition (wt.Particle Mesh Size (US. Standard Sieve) Particle gauge (mils) 113.1111).percent) (Percent of metal component) Mg Si Al 20/+40 40/+100 1 200 11/5 5/20 10/15 15/20 20 1 1 Substantially all between 20 and 40 mils.

TABLE IV.-EXPLOSIVE TEST RESULTS Run Peak Pressure Shock Energy BubbleEnergy Total Energy N0. (lbs/sq. in.) (Kcal./gm.) (KcaL/gm.) (KcaL/gm.)

3, 487 O. 72 0. 68 1. 40 3, 675 0. 73 0. 68 1. 41 3, 785 0. 84 0. 67 1.51 3, 483 0. 72 0. 68 1. 4O 3, 599 0. 73 0. 69 1. 42 3, 519 0. 77 0.69 1. 46 3, 442 0. 67 0. 66 1. 33 3, 475 0. 67 0. 67 1. 33 3, 505 0. 750. 69 1. 44 3, 552 0. 80 0. 67 l. 47 3, 429 0. 68 0. 68 1. 36 3, 813 0.77 0. 68 1. 45

Various modifications can be made in the present invention withoutdeparting from the spirit or scope thereof for it is understood that Ilimit myself only as defined in the appended claims.

I claim:

1. A dry explosive composition consisting essentially of, on a weightbasis:

(a) particulate ammonium nitrate from about 50 to about 97 percent;

(b) particulate light metal from about 3 to about 50 percent, said lightmetal ranging substantially from about No. 4 to No. 200 mesh US.Standard Sieve and having a gauge of from about 0.25 mil to about 40mils;

() up to about 40 percent of an inorganic oxidizing salt selected fromthe group consisting of particulate alkali metal nitrate, chlorate,perchlorate and mixtures thereof;

(d) up to about percent of non-detonable organic fuel; and

(e) up to about 2.5 percent of a member selected from the groupconsisting of gelling or thickening agents.

2. The dry explosive composition as defined in claim 1 wherein theparticulate metal has a particle size distribution of from about 25 toabout 60 percent larger than about No. 50 mesh, the balance beingsubstantially No. 50 to about No. 100 mesh and from about to 100 percentof the particles have a gauge of from about 0.25 mil to about 4 mils andup to about 85 percent have a gauge of from about 4 to about 15 mils.

3. The dry explosive composition as defined in claim 1 wherein theparticulate metal has a gauge of less than about 10 mils.

4. The dry explosive composition as defined in claim 1 which includes inaddition up to about 16 percent of a detonable organic sensitizer.

5. The dry explosive composition as defined in claim 1 wherein theparticulate ammonium nitrate ranges from about to 95 percent; theparticulate light metal is a member selected from the group consistingof particulate aluminum, magnesium, magnesium alloys, aluminum alloysand mixtures thereof; the inorganic oxidizing salt consists of up toabout 25 percent of sodium nitrate; the non-detonable organic fuelsconsist of up to about 6 percent of non-detonable liquid hydrocarbons;and said gelling or thickening agent consists of natural gums, syntheticpolymeric thickening agents or mixtures up to about 1 percent.

6. The dry explosive composition as defined in claim 5 wherein saidnon-detonable liquid hydrocarbon consists of fuel oil.

7. The dry explosive composition as defined in claim 5 wherein theparticulate metal has a particle size distribution of from about 25 toabout percent larger than about No. 50 mesh, the balance beingsubstantially N0. 5 0 to about No. 100 mesh and from about 15 to 100percent of the particles having a gauge of from about 0.25 mil to about4 mils and up to about percent have a gauge of from about 4 to about 15mils.

8. The dry explosive composition as defined in claim 5 wherein theparticulate metal has a gauge of less than about 10 mils.

9. The dry explosive composition as defined in claim 5 which includes inaddition up to about 16 percent of a detonable organic sensitizer.

References Cited UNITED STATES PATENTS 3,255,058 6/1966 Wyman et al 149114 X 3,307,986 3/1967 Grant 14944 X 3,331,717 7/1967 Cook et a1. 14943 XCARL D. QUARFORTH, Primary Examiner.

S. J. LECHERT, Assistant Examiner.

U.S. c1. X.R.

